JP5216481B2 - Overcurrent protection device - Google Patents

Description

  The present invention relates to an overcurrent protection device that protects an electric compressor used in a cooling device such as a refrigerator or a small air conditioner from burning due to an overcurrent that occurs in an overload state or a locked state.

  Conventionally, in order to protect an electric compressor used for a cooling device such as a refrigerator and a small air conditioner from an overcurrent state, the electric compressor is closely attached to a main body case of the electric compressor, senses temperature, and is used as an electric motor of the electric compressor. An overcurrent protection device that opens and closes a switch contact piece connected in series between the electric motor of the electric compressor and the power source is provided using a bimetal that operates by the heat of the heater that generates heat in response to the flowing overcurrent. ing. In this case, when the operating temperature of the bimetal is reached due to the abnormal temperature of the main body case of the electric compressor or the heating of the heater in an overcurrent state, the bimetal is reversed in reverse, thereby opening the switch piece, While energizing is interrupted, energization to the heater is also interrupted. And when it cools to the return temperature of a bimetal by natural cooling, a bimetal will reverse reverse (return reverse), a switch contact piece will close, and electricity supply to the motor of an electric compressor and electricity supply to a heater will be restarted.

  In this way, the bimetal inversion operation prevents the electric compressor from being burned out, but when the electric compressor is overloaded or locked, the bimetal inversion and reverse inversion are repeated, Along with this, the switch piece opens and closes, but if this is done for a long time, the bimetal's forward / reverse life will end, and the bimetal will not be able to open the switch piece. Is welded, the electric motor of the electric compressor remains in an overcurrent state, and the electric motor is burned out.

  In order to solve such a problem, the connection contact piece having a contact for opening and closing the energization circuit to the electric motor of the electric compressor is opened by reversing the first bimetal contact piece in a normal overcurrent state, Shut off the energizing circuit. Then, when the life of the first bimetal piece is exhausted and the reversing operation is not performed, an overcurrent continues to flow to the electric motor of the electric compressor. However, due to the high temperature at that time, the second bimetal piece is It reverses and the said connection piece is opened, and the electricity supply circuit to the electric motor of an electric compressor is opened. The return temperature of the second bimetal contact piece is set to a temperature that does not return in a normal environment, such as −50 ° C., and once the operation is performed, energization to the electric motor of the electric compressor is continued. There is a technology having a so-called fail-safe function for preventing the electric motor from burning. (For example, patent document 1).

  In addition, the thermo bimetal is reversed by the abnormal temperature of the main body case of the electric compressor, the thermo switch part opens the energization circuit to the electric motor of the electric compressor, and the heater generates heat due to the overcurrent to the electric motor of the electric compressor. Case where the bimetal is reversed, the main bimetal movable contact opens from the fixed contact, the protector part that opens the energization circuit to the motor of the electric compressor is formed, and the thermo switch part, protector part and heater are made of one insulator And an adjustment screw for attaching the center portion of the main bimetal and the main bimetal are joined by a hot-melt metal (solder). (For example, Patent Document 2)

In this patent document 2, the main bimetal normally reverses and opens an energization circuit to the motor of the electric compressor. However, when the movable contact of the main bimetal is welded to the fixed contact, the heater continues to generate heat. When the temperature inside the case rises and the molten metal (solder) melts, the coupling between the adjustment screw and the main bimetal is broken, and the main bimetal is forced down by the coil spring attached to the adjustment screw, and it can be moved from the fixed contact. It has a so-called fail-safe function in which the contacts are forcibly peeled off.
Japanese Patent Application Laid-Open No. 07-201262 JP 09-180612 A

  Both of the technology of Patent Document 1 and the technology of Patent Document 2 are heaters that are generated when a contact that opens a current-carrying circuit to an electric motor of an electric compressor to prevent the electric motor from burning due to an overcurrent is welded for some reason. This is common in that the welded contacts are forcibly peeled off by the heat generated so that the non-energized state of the electric motor is continued and burnout is prevented.

  However, since the technique of Patent Document 2 is a mechanism in which the molten metal (solder) is melted and the movable contact is forcibly removed from the fixed contact, the operation time point for forcibly removing the movable contact from the fixed contact is It is affected by the melting temperature of hot-melt metal (solder). That is, the melting time differs depending on the bonding state and material of the hot-melt metal (solder), and it is difficult to determine the desired time when the movable contact is peeled off from the fixed contact.

  In the technique of Patent Document 2, since the molten metal (solder) is melted and the movable contact is forcibly removed from the fixed contact, once the operation is performed, it cannot be returned and reused. In order to restart the electric compressor, the overcurrent protection device must be replaced. In addition, since the movable contact is forcibly peeled off from the fixed contact, there is a concern about the state where the contact is not peeled off when the welding is strong.

  Since the technique of Patent Document 1 is not a technique in which hot-melt metal (solder) is melted as in Patent Document 2, the second bimetal contact piece that has once reversed is cooled to a return temperature of, for example, −50 ° C. or lower. Then, since it will return and it will be in a reusable state, the problem which becomes unusable like patent document 2 will be solved.

  However, in Patent Document 1, a second bimetal contact piece connected and fixed by welding or the like is provided at the tip of a conductive piece attached and fixed to a fixed terminal and extending horizontally, and a first bimetal contact piece is provided below the second bimetal contact piece. Further, a heater is disposed below the heater. When a normal overcurrent occurs, the first bimetal contact piece is inverted upward by the heat generated by the heater, and the conductive piece is pushed upward, whereby the movable contact of the second bimetal contact piece is separated from the fixed contact, and the electric compressor Shut off the current supply circuit. When the movable contact of the second bimetal contact is welded to the fixed contact, the second bimetal contact is inverted upward due to the increase in heat generated by the heater, and the movable contact of the second bimetal contact is peeled off from the fixed contact. The current supply circuit to the electric compressor is shut off.

  However, the part that interrupts the current supply circuit to the electric compressor is only the movable contact portion of the second bimetal contact piece, and the first bimetal contact piece pushes the conductive piece upward to move the second bimetal contact piece. Since the contact is separated from the fixed contact, it is difficult to set operation conditions such as the acting force of the second bimetal contact piece, and the structure is complicated. In addition, since the movable contact is forcibly peeled off from the fixed contact, there is a concern about the state where the contact is not peeled off when the welding is strong.

  In view of such a point, the present invention continuously provides a contact portion that opens and closes a current supply circuit to the electric compressor during a normal overcurrent and a current supply circuit to the electric compressor when the contact portion is welded. An overcurrent protection device is provided in which the contact portions that are opened separately are configured separately, and the operating conditions are easily designed and the structure is simplified. Also provided is an overcurrent protection device that is reusable.

An overcurrent protection device according to a first aspect of the present invention is an overcurrent protection device connected in series with the electric compressor to a current supply circuit to the electric compressor, wherein a bottomed cylinder whose one surface is an opening covered with a heat conductive plate In a heat-resistant insulating case having a shape , the current supply circuit to the electric compressor is shut off at a temperature equal to or higher than the first temperature, and the first temperature is returned to a return temperature lower than the first temperature and higher than 0 ° C. A first overcurrent relay section comprising a first bimetal contact piece provided with a first movable side contact that opens and closes with respect to the fixed contact of the projecting portions on both the left and right sides of the circular bimetal plate ; A second movable contact that opens and closes the second fixed contact so that the current supply circuit to the electric compressor is cut off at a second temperature higher than the temperature and the electric compressor is restored only at a temperature lower than 0 ° C. In the same manner as the first bimetal contact piece. A second overcurrent relay section of the second bimetal contact piece provided in the protruding portions of the left and right sides of Le plate, the first fixed contact and the second fixed contact at an angle placement of approximately 90 degrees The first bimetal contact piece and the second bimetal contact piece are disposed and electrically form a series circuit, and the first bimetal contact piece is located closer to the opening than the second bimetal contact piece. The first bimetal contact piece and the second bimetal contact piece are spaced apart from each other, and a central portion is supported in an electrically insulated state on a support shaft provided on the bottom wall of the case, and the opening is the electric compressor When the first bimetal contact piece is heated to the first temperature or higher, the first movable side contact is separated from the first fixed contact, and the second movable contact is separated from the first fixed contact. Bimetal contact piece is the first movable Wherein the contact is a relationship that the inverted second movable contact is separated from the second fixed contact by being heated to more than welded the second temperature to the first fixed contact.

The overcurrent protection device according to a second aspect of the present invention is the overheat protection device according to the first aspect, wherein an electric heater that is connected in series to the series circuit and generates heat due to an overcurrent supplied to the electric compressor is provided in the heat resistant insulation case. The second bimetal contact piece and the bottom wall of the case are housed in a thermal coupling relationship with the first bimetal contact piece and the second bimetal contact piece.

  In the first invention, the overcurrent protection device is configured by connecting the first overcurrent relay unit and the second overcurrent relay unit in series, and the first overcurrent relay unit 2 and the second overcurrent relay unit 3 have substantially the same configuration. Therefore, since the desired overcurrent protection device 1 can be achieved by setting the angle arrangement to approximately 90 degrees, the structure is simple, the operating conditions can be easily designed, and the assembly can be easily performed. Further, since the welded movable contact is not forcibly removed, even when welding is strong, the electric compressor can be stably shut off. Furthermore, once it has been operated, it can be reused if it is cooled below the return temperature, which is economical.

  In the second invention, the temperature of the first bimetal contact piece or the second bimetal contact piece is reversed by the heat generated by the electric heater caused by the overcurrent supplied to the electric compressor while the effects of the first invention are achieved. This is preferable as an overcurrent protection device based on both sensing and overcurrent detection.

The overcurrent protection device of the present invention is an overcurrent protection device connected in series with the electric compressor to a current supply circuit to the electric compressor, and has a bottomed cylindrical shape whose one surface is an opening covered with a heat conductive plate In the one heat-resistant insulating case forming the first, the current supply circuit to the electric compressor is cut off at a temperature equal to or higher than the first temperature, and the first temperature is returned to a return temperature lower than the first temperature and higher than 0 ° C. A first overcurrent relay portion comprising a first bimetal contact piece provided with a first movable side contact that opens and closes with respect to the fixed contact on the left and right projecting portions of the circular bimetal plate; and the first temperature A second movable contact that opens and closes the second fixed contact so as to cut off the current supply circuit to the electric compressor at a temperature higher than the second temperature and return only at a temperature lower than 0 ° C. A circular bimeta like the first bimetal contact piece. A second overcurrent relay section of the second bimetal contact piece provided in the protruding portions of the left and right sides of the plate, the first fixed contact and the second fixed contact at an angle placement of approximately 90 degrees The first bimetal contact piece and the second bimetal contact piece are arranged and electrically constitute a series circuit, and the first bimetal contact piece is closer to the opening side than the second bimetal contact piece. The first bimetal contact piece and the second bimetal contact piece are spaced apart and the center part is supported in an electrically insulated state by a support shaft provided on the bottom wall of the case, and the opening is on the electric compressor side When the first bimetal contact piece is heated to the first temperature or higher, the first movable contact is separated from the first fixed contact, and the second bimetal is attached. The contact piece is the first movable side Point a relationship away from the first welded to the fixed contact reversed and the second movable side contact the second fixed contact by being heated to above the second temperature, embodiments of the present invention Is described below.

  FIG. 1 is a circuit diagram in which a first overcurrent relay unit and a second overcurrent relay unit constituting an overcurrent protection device according to the present invention are connected in series, and FIG. 2 shows an appearance of the overcurrent protection device according to the present invention. FIG. 3 is a side view of the overcurrent protection device shown in FIG. 2, and FIG. 4 is an internal configuration diagram of the overcurrent protection device shown in FIG. FIG. 6 is a view showing a state in which the overcurrent protection device according to the present invention is housed in a cover and attached to the upper surface of the sealing case of the electric compressor, and FIG. 6 is a diagram showing the state where the overcurrent protection device according to the present invention is housed in the cover and the electric compressor is sealed. FIG. 7 is a cross-sectional view taken along line AA in FIG. 4 and FIG. 8 is a cross-sectional view taken along line BB in FIG.

  The overcurrent protection device 1 of the present invention is attached in close contact with the main body case 51 of the electric compressor 50 in order to protect the electric compressor 50 used in a cooling device such as a refrigerator or a small air conditioner from its overcurrent state. It operates to sense the temperature and cut off the energization of the motor 52 in accordance with the overcurrent flowing through the motor 52 of the electric compressor 50. In the electric compressor 50, a motor 52 and a refrigerant compressor unit 53 are housed in a main body case 51 constituting a sealed case, and the refrigerant compressor unit 53 is driven by the electric motor 52 to compress refrigerant. It is.

  The overcurrent protection device 1 is configured to be connected in series with the electric motor 52 to a current supply circuit to the electric motor 52 of the electric compressor 50, and the first overcurrent relay unit 2 and the second overcurrent relay unit 3 are electrically connected. It is the structure connected in series and accommodated in the heat-resistant insulating case 1K made of synthetic resin.

  The overcurrent protection device 1 shuts off the current supply circuit to the motor 52 of the electric compressor 50 at a temperature equal to or higher than the first temperature (T1 ° C.) in one heat-resistant insulating case 1K made of synthetic resin. A first bimetal contact piece 2A comprising a first movable contact 2E that opens and closes with respect to the first fixed contact 2G so as to return at a return temperature lower than (T1 ° C.) and higher than 0 ° C. 1 Overcurrent relay unit 2 and the current supply circuit to the motor 52 of the electric compressor 50 are cut off at a temperature equal to or higher than the second temperature (T2 ° C) higher than the first temperature (T1 ° C) and lower than 0 ° C. A second overcurrent relay unit 3 is provided that includes a second bimetal contact piece 3A having a second movable contact 3E that opens and closes with respect to the second fixed contact 3G so as to return only at a temperature (T3 ° C.). The first overcurrent relay unit 2 and the second overcurrent relay unit 3 are approximately 90 degrees. At an angle arrangement, a first overcurrent relay unit 2 and the second over-current relay unit 3 is obtained by constituting the electrical series circuit. For this reason, the first fixed contact 2G and the second fixed contact 3G are arranged at an angle of about 90 degrees, and the first bimetal contact piece 2A and the second bimetal contact piece 3A electrically form a series circuit. Yes.

  This will be specifically described below. As shown in FIGS. 1 to 4, a heat-resistant insulating case 1K made of a synthetic resin having a bottomed cylindrical shape whose one surface (the lower surface in FIG. 2) is an opening 1K1 is mainly used, and the bottom wall of the case 1K (FIG. 2). The first bimetal contact piece 2A and the second bimetal contact piece 3A are spaced apart from the inner surface of the case 1K on the support shaft 2C fixed to the center portion of the 1K2 with the nut 2D. Supported in a laminated state. Since the first bimetal contact piece 2A and the second bimetal contact piece 3A are preferably electrically insulated from each other, in the embodiment, the first bimetal contact piece 2A and the second bimetal contact piece through the support shaft 2C. The support shaft 2C is formed of an electrical insulator such as a synthetic resin so that the 3A is not energized.

  The bimetal contact piece 2A includes movable side contacts 2E at the left and right projecting portions of a circular bimetal plate. Further, the bimetal contact piece 3A includes movable side contacts 3E on the left and right projecting portions of a circular bimetal plate. Two external terminals A and B are attached to the bottom wall (upper side wall in FIG. 2) 1K2 of the case 1K, and the external terminals A and B are exposed inside the case 2K.

  A terminal C is provided on the inner side of the bottom wall (upper side wall) 1K2 of the case 1K, and the inner wall of the bottom wall (upper side wall) 1K2 is connected to the left and right movable contacts 2E of the bimetal contact piece 2A. A corresponding first fixed contact 2G and a second fixed contact 3G respectively corresponding to the left and right movable contacts 3E of the bimetal contact piece 3A are provided. One fixed contact 2G is formed at the inner end of the external terminal A, and one fixed contact 3G is formed at the terminal C.

  In the case 1K, the first overcurrent relay unit 2 and the second overcurrent relay unit 3 are arranged at an angle of approximately 90 degrees, and the first overcurrent relay unit 2 and the second overcurrent relay unit 3 are electrically connected in series. Is configured. For this reason, the first fixed contact 2G and the second fixed contact 3G are arranged at an angle of about 90 degrees, and the first bimetal contact piece 2A and the second bimetal contact piece 3A electrically form a series circuit. Yes.

  Further, the overcurrent protection device 1 includes terminals B, C (in the case 1K so that the electric heater 1B having a predetermined electric resistance is in a thermal coupling relationship with the bimetal contact piece 2A and the bimetal contact piece 3A. One fixed contact 3G) is disposed along the inner surface of the bottom wall (upper side wall in FIG. 2) 1K2.

  A specific example of the arrangement configuration of the first bimetal contact piece 2A and the second bimetal contact piece 3A is shown in FIG. 4, FIG. 7 and FIG. As shown in FIG. 4, the pair of fixed contacts 2G and 2G are arranged on the left and right axis, the pair of fixed contacts 3G and 3G are arranged on the vertical axis, and the movable side contacts 2E and 3E correspond to this. As described above, the bimetal contact piece 2A and the bimetal contact piece 3A are arranged on the support shaft 2C with a space between the insulating insulator spacers S1 and S2. As shown in FIGS. 7 and 8, the bimetal contact piece 2A, the bimetal contact piece 3A, and the electric heater 1B are sequentially connected from the opening 1K1 side of the case 1K toward the bottom wall (upper side wall) 1K2 of the case 1K. Are arranged at intervals. The opening 1K1 is covered with a heat conducting plate 1P.

  In a normal state that is not an overcurrent state, the bimetal contact piece 2A is in a state where the left and right movable contact points 2E are in contact with the left and right fixed contact points 2G, as shown by the solid line in FIG. As shown by a solid line in FIG. 1, the left and right movable contacts 3E are in contact with the left and right fixed contacts 3G.

  As shown in FIGS. 5 and 6, the overcurrent protection device 1 has an opening 1K1 in a state where the first bimetal contact piece 2A, the second bimetal contact piece 3A, and the electric heater 1B are disposed in the case 1K. It is configured to be stored in a predetermined cover KS with the side facing downward, and this cover KS is attached to the upper surface of the main body case 51 of the electric compressor 50, and an external terminal for power supply stored in the cover KS 57 is connected to the terminals 54A, 54B and 54C protruding from the upper surface of the main body case 51, and the bimetal contact pieces 2A and 3A are in a state of sensing the temperature of the main body case 51. In this attached state, the bimetal contact piece 2A is positioned below the bimetal contact piece 3A, so that the temperature of the main body case 51 can be easily detected.

  In the cover KS, the overcurrent protection device 1 is accommodated on one side, and the external terminal 57 is accommodated on the other side. The structure in which the cover KS is attached to the upper surface of the main body case 51 is such that the engagement holes 60A and 60B are formed in the left and right engaging pieces of the metal support base 59 attached to the upper surface of the main body case 51, 58A and 58B are attached to the corresponding locking holes 60A and 60B by being locked by the elasticity of the cover KS, respectively. As a result, the opening 1K1 of the case 1K comes into contact with the support base 59.

  As shown in FIG. 1, in the overcurrent protection device 1 having the above configuration, the first bimetal contact piece 2A, the second bimetal contact piece 3A, and the electric heater 1B electrically form a series circuit. A circuit is connected in series with the electric motor 52 of the electric compressor 50. Further, in the overcurrent protection device 1 of the type not provided with the electric heater 1B, the first bimetal contact piece 2A and the second bimetal contact piece 3A electrically form a series circuit, and this series circuit is an electric compressor. 50 electric motors 52 are connected in series.

  One specific circuit connection is described below. The electric motor 52 shown in FIG. 1 shows the case of an AC electric motor, and the power source 55 is also an AC power source. If the electric motor 52 is controlled by an inverter whose rotation speed is variable by frequency conversion, the power source 55 is an inverter-controlled power source.

  One terminal 54C of the electric motor 52 is connected to the power supply 55, and the overcurrent protection device 1 has the other terminal 54A of the electric motor 52 connected to the terminal A (corresponding to the fixed contact 2G of the first overcurrent relay unit 2). The bimetal contact piece 2A in which the movable contact 2E is in contact with the fixed contact 2G, the bimetal contact piece 3A in which the movable contact 3E is in contact with the fixed contact 3G, and the electric heater 3B form an electrical series circuit. , Terminal B is connected to terminal 54B connected to power supply 55. For this reason, the series circuit of the 1st overcurrent relay part 2 and the 2nd overcurrent relay part 3 is connected to the electric motor 52 in series.

  In this configuration, during normal operation of the electric compressor 50, the current flowing through the electric motor 52 is less than the set value, so that the amount of heat generated from the electric heater 1B increases as the bimetal contact piece 2A is reversed as indicated by the dotted line in FIG. Further, the amount of heat generated from the electric heater 1B is not so large that the bimetal contact piece 3A is reversed as shown by the dotted line in FIG. 1, and the temperature of the main body case 51 is also shown by the dotted line in FIG. Therefore, the motor 52 is in a state of supplying power from the power source 55 while maintaining the state in which the movable contact 2E is in contact with the fixed contact 2G and the movable contact 3E is in contact with the fixed contact 3G. The electric compressor 50 continues the normal operation state.

  However, when the electric compressor 50 is overloaded, or when the electric compressor 50 is in a starting failure or locked state, the amount of heat received by the bimetal contact pieces 2A and 3A increases due to the temperature rise of the electric compressor 50. Further, when an overcurrent exceeding the set value flows, the amount of heat generated by the electric heater 1B increases, and the amount of heat received by the bimetal contact pieces 2A and 3A increases. As a result, the bimetal contact piece 2A is first heated to a first temperature (T1 ° C.... 120 ° C.) or higher, which is the operating temperature, so that the bimetal contact piece 2A is inverted as shown by the dotted line in FIG. The movable contact 2E is separated from the fixed contact 2G and interrupts the current supply circuit to the motor 52. Since the reversal operation temperature of the bimetal contact piece 3A is set to be considerably higher than the first temperature (T1 ° C.), the reversal operation is not performed, and the movable contact 3E remains in contact with the fixed contact 3G. It is.

  Thus, when the electric compressor 50 is stopped, the electric heater 1B is not energized, and due to natural cooling, the return temperature (for example, 120 ° C.) is lower than the first temperature (T 1 ° C.... 120 ° C.). 100 ° C.), the bimetal contact piece 2A reversely reverses (returns) as shown by the solid line in FIG. 1, the movable contact 2E comes into contact with the fixed contact 2G again, and the electric motor 52 is activated again to start the electric compressor 50. Returns to the operating state. At this time, if the overload state of the electric compressor 50, or the start-up failure or the locked state is eliminated, the electric current flowing through the electric motor 52 is less than the set value, so that the electric compressor 50 is normal as described above. Continue operating. However, when the electric compressor 50 is restored, if the overload state or the start-up failure or the locked state is not eliminated, the bimetal contact piece 2A is heated again to the first temperature (T1 ° C.) that is the operating temperature. As a result, the bimetal contact piece 2A is reversed as indicated by the dotted line in FIG. 1, and the movable contact 2E is separated from the fixed contact 2G, thereby interrupting the current supply circuit to the motor 52. In this way, the electric compressor 50 is protected from an overload state, or burnout caused by a starting failure or a locked state.

  However, when the number of times of opening / closing the movable contact 2E with respect to the fixed contact 2G by reversing and returning the bimetal contact piece 2A is performed over a long period of time, or when the electric compressor 50 is operated over a long period of time, the fixed contact The opening / closing frequency of the movable contact 2E with respect to 2G increases, the life of the bimetal contact piece 2A reaches the normal reversal / reverse reversal, the movable contact 2E cannot be opened with respect to the fixed contact 2G, and the movable contact 2E When welding to the fixed contact 2G, the electric motor 52 of the electric compressor 50 remains in an overcurrent state, and if this continues, the electric motor 52 is burned out.

  Thus, when the movable contact 2E is welded to the fixed contact 2G, energization to the electric heater 1B is continued, so the amount of heat generated by the electric heater 1B increases and the amount of heat received by the bimetal contact piece 3A increases. As a result, the bimetal contact piece 3A is heated to a second temperature (T2 ° C.... 150 ° C.) or higher, which is the operating temperature, so that the bimetal contact piece 3A is inverted as shown by the dotted line in FIG. The movable contact 3E moves away from the fixed contact 3G, interrupts the current supply circuit to the electric motor 52, and prevents the electric motor 52 from burning out.

  The second temperature (T2 ° C.), which is the operating temperature at which the bimetallic contact piece 3A is inverted and the movable contact 3E is separated from the fixed contact 3G, is reversed and the movable contact 2E is separated from the fixed contact 2G. Since the temperature is set to be considerably higher than the first temperature (T1 ° C.... 120 ° C., for example, 120 ° C.), for example, 150 ° C., the bimetal contact piece 3A is reversed before the bimetal contact piece 2A is reversed. It will not work.

  The return temperature at which the movable contact 3E comes into contact with the fixed contact 3G again when the bimetal contact piece 3A reversely reverses (returns) as shown by the solid line in FIG. 1 is set to a temperature sufficiently lower than 0 ° C. (T3 ° C.). This temperature is a sub-zero temperature (T3 ° C.) that is sufficiently lower than the low temperature that occurs in the temperature situation where the electric compressor 50 is used in a normal environment. Since T3 ° C. is several tens of degrees below zero, for example, about −50 ° C., once the bimetal contact piece 3A is reversed as shown by the dotted line in FIG. 1, the bimetal contact piece 3A is artificially brought up to this return temperature. Since it will not return unless it is cooled, once the bimetal contact piece 3A is reversed as shown by the dotted line in FIG. 1, it will not return permanently, so the burnout protection of the electric compressor 50 continues. Will be. The method of cooling the bimetal contact piece 3A to the return temperature can be used again if it is cooled by liquid nitrogen or a low-temperature refrigeration apparatus.

  In the above, since the electrical resistance of the bimetal contact pieces 2A and 3A is considerably smaller than the electrical resistance of the electric heater 1B, the self-heating of the bimetal contact pieces 2A and 3A in a state where an overcurrent flows is small, and the overcurrent is small. The reversal operation when it flows is substantially due to the heat generated by the electric heater 1B.

  As described above, since the first overcurrent relay unit 2 and the second overcurrent relay unit 3 have substantially the same configuration and are arranged at an angle of about 90 degrees, the desired overcurrent protection device 1 can be achieved. It is structurally simple, easy to design operating conditions, and easy to assemble.

  FIG. 1 shows circuit connections of the power source 55, the electric motor 52, the first overcurrent relay unit 2, the second overcurrent relay unit 3, and the electric heater, but the first overcurrent relay unit 2 and the second overcurrent are shown. The connection which forms the series circuit which switches the position of the relay 3 and an electric heater and performs a function similarly to the above may be sufficient.

  In the above description, the bimetal contact piece 2A of the first overcurrent relay unit 2 and the bimetal contact piece 3A of the second overcurrent relay unit 3 together with the temperature detection of the main body case 51 of the electric compressor 1 generate heat of the electric heater 1B. However, the electric heater 1B may be omitted, and the reverse operation may be performed only by sensing the temperature of the main body case 51.

  In the above description, the bimetal contact piece 2A of the first overcurrent relay unit 2 and the bimetal contact piece 3A of the second overcurrent relay unit 3 sense the temperature of the main body case 51 of the electric compressor 1. The bimetal contact pieces 2A and 3A may be reversely operated only by the amount of heat generated by the electric heater 1B.

  In the present invention, the configuration of the electric compressor 1, the configurations of the first overcurrent relay 2 and the second overcurrent relay 3 and the like are not limited to the above-described embodiment, and various modifications can be made without departing from the technical scope of the present invention. Are contemplated and encompass various embodiments.

It is the circuit diagram by which the 1st overcurrent relay part and the 2nd overcurrent relay part which comprise the overcurrent protection apparatus which concern on this invention were connected in series. It is a side view which shows the external appearance of the overcurrent protection apparatus which concerns on this invention. It is a figure which shows the external appearance by the side of the terminal part of the overcurrent protection apparatus shown in FIG. It is an internal block diagram seen from the opening surface of the overcurrent protection apparatus shown in FIG. It is a figure which shows the state which accommodated the overcurrent protection apparatus which concerns on this invention in the cover, and was attached to the upper surface of the airtight case of an electric compressor. FIG. 3 is a specific exploded perspective view of a portion where the overcurrent protection device according to the present invention is housed in a cover and attached to the upper surface of the sealed case of the electric compressor. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Overcurrent protection device 2 ... 1st overcurrent relay 2A ... Bimetal contact piece 2B ... Electric heater 2C ... Support shaft 2E ... Movable contact 2G ... Fixed Contact 2K ・ ・ ・ Heat-resistant insulation case 3 ・ ・ ・ Second overcurrent relay 3A ・ ・ ・ Bimetal contact piece 3B ・ ・ ・ Electric heater 3C ・ ・ ・ Support shaft 3E ・ ・ ・ Moving side contact 3G ・ ・ ・ Fixed contact 3K: heat-resistant insulation case 50 ... electric compressor 51 ... main body case 52 ... electric motor 53 ... compression section 55 ... power supply

Claims (2)

In the overcurrent protection device connected in series with the electric compressor to the electric current supply circuit to the electric compressor, in one heat-resistant insulating case having a bottomed cylindrical shape whose one surface is an opening covered with a heat conductive plate , the opened and closed with respect to the first fixed contact so as to return at higher return temperatures than the 0 ℃ lower than interrupts the current supply circuit to the electric compressor of the first temperature at a first temperature or more A first overcurrent relay portion comprising a first bimetal contact piece provided with one movable-side contact on the left and right projecting portions of a circular bimetal plate, and a second temperature higher than the first temperature The second movable contact that opens and closes the second fixed contact so as to cut off the current supply circuit to the electric compressor and return only at a temperature lower than 0 ° C. is the same as the first bimetal contact piece. On the left and right protrusions of a circular bimetal plate The second includes a second over-current relay unit consisting of bimetal contact pieces, the said first of the said fixed contact second fixed contact at an angle placement of approximately 90 degrees first bimetal contact piece No. And the first bimetal contact piece and the second bimetal contact piece are located closer to the opening side than the second bimetal contact piece. In a mounted state in which the bimetal contact piece of 2 is supported in an electrically insulated state on a support shaft provided on the bottom wall of the case with a gap therebetween, and the opening is on the electric compressor side, When the bimetal contact piece is heated to the first temperature or more, it is reversed and the first movable contact is separated from the first fixed contact, and the second bimetal contact piece is the first movable contact. Side contact is the first fixed contact Overcurrent protection apparatus characterized by destination and the second movable contact is inverted by being heated to above the second temperature is related away from the second fixed contact. An electric heater that is connected in series to the series circuit and generates heat due to an overcurrent supplied to the electric compressor is disposed between the second bimetal contact piece and the bottom wall of the case. The overcurrent protection device according to claim 1 , wherein the first bimetal contact piece and the second bimetal contact piece are housed in a thermally coupled relationship.

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